1. Field of the Invention
The present invention relates to a vehicular radar, in particular a vehicular radar with a reflector, which is mounted on a vehicle, such as an automobile, to measure, e.g., the distance between a driving vehicle and an object.
2. Discussion of Background
In FIG. 3 is shown a schematic view to explain an antenna unit employed in a conventional vehicular radar, which is mounted on a vehicle, such as an automobile.
As schematically shown in FIG. 3, the conventional antenna unit includes a plurality of electromagnetic radiators 8a, which are provided at suitable positions with respect to a lens 21 so as to have a certain beamwidth and a certain beam spacing. The electromagnetic radiators are sequentially switched to change a beam radiating direction to successively measure a certain range, detecting an object in front of the vehicle.
There is an antenna unit that includes many antenna wherein the transmitting phase and the transmitting output of the respective antennas are controlled to change a beam radiating direction as a whole so as to scan a certain range, detecting an object in front of the vehicle.
Since the conventional vehicular radars carry out control by sequentially switching the plural electromagnetic radiators, the conventional vehicular radars have created a problem in that a great decrease in output is caused at a switching controller to degrade efficiency.
A radiant beam is required to be narrowed in order to radiate the electromagnetic wave to a lens in effective fashion. Narrowing the radiant beam requires that the electromagnetic radiators be enlarged. When the plural electromagnetic radiators are provided, the beam spacing can not be set to not greater than a certain value since the spacing between adjoining electromagnetic radiators is expanded. When electromagnetic radiators are provided at narrow intervals in order to obtain a certain beam spacing, the electromagnetic radiators are required to be small, resulting in expansion in the radiant beam radiated from each of the electromagnetic radiators. This means that the number of the radiant beams that pass outside the lens increases and that the number of the radiant beams that pass through the lens decreases, creating a problem in that the efficiency degrades.
It is an object of the present invention to solve these problems, and to provide a vehicular radar including an antenna unit comprising a single electromagnetic radiator for radiating a transmitted electromagnetic wave, a single reflector for reflecting the transmitted electromagnetic wave from the electromagnetic radiator and radiating the transmitted electromagnetic wave as a beam and a reflector swinging device for swinging the reflector so as to have successively change a direction of the electromagnetic wave beam, thereby easily setting the beamwidth and the beam spacing of the radiated beam at certain values and radiating the radiated beam in a certain direction with a high efficiency and at stable fashion.
The present invention provides a vehicular radar comprising a transmitter for outputting a transmitted electromagnetic wave, an antenna unit for radiating the transmitted electromagnetic wave and receiving a electromagnetic wave reflected by an object to be detected as a received electromagnetic wave, a receiver for detecting the reflected electromagnetic wave received by the antenna unit, and a signal processor for processing an output signal from the receiver to output information about the object, wherein the antenna unit comprises a single electromagnetic radiator for radiating the transmitted electromagnetic wave, a single reflector for reflecting the transmitted electromagnetic wave from the electromagnetic radiator and radiating the transmitted electromagnetic wave as a beam, and a reflector swinging device for swinging the reflector so as to successively change a direction of the beam.
The electromagnetic radiator may be fixed at a certain location, and the reflector swinging device may swing the reflector so as to have a focus of the reflector located at the certain location.
The reflector swinging device may support the reflector so as to have a focus of the reflector located on a swinging axis of the reflector swinging device. In addition, the reflector swinging device may comprise a reflector supporting arm with a cam follower provided on an imaginary line crossing the swinging axis, and a cam engaged with the cam follower to swing the reflector supporting arm in a certain angular range. The electromagnetic radiator may be fixed on the swinging axis.
The vehicular radar may further comprise an urging member having an end fixed to a stationary portion and the other end fixed to the reflector supporting arm to press the cam follower against the cam.
The urging member may comprise a coiled spring.
The reflector may be a molded product made of a plastic material and having a metallic film provided thereon.
The electromagnetic radiator may be an injection-molded product made of a magnesium alloy.
As explained, the present invention can radiate the transmitted electromagnetic wave to the reflector with
When the electromagnetic radiator is fixed at a certain location, and when the reflector swinging device swings the reflector so as to have the focus of the reflector located at the certain location, the beam radiated from the electromagnetic radiator and reflected by the reflector can be radiated at a certain beam spacing and with a stable strength.
When the reflector swinging device supports the reflector so as to have the focus of the reflector located on the swinging axis of the reflector swinging device, when the reflector swinging device comprises the reflector supporting arm with the cam follower provided on the imaginary line crossing the swinging axis, and the cam engaged with the cam follower to swing the reflector supporting arm in a certain angular range, and when the electromagnetic radiator is fixed on the swinging axis, the reflector swinging device can be made smaller.
When the vehicular radar further comprises the urging member having an end fixed to a stationary portion and the other end fixed to the reflector supporting arm to press the cam follower against the cam, the reflector can be swung in stable fashion.
When the reflector is a molded product made of a plastic material and having a metallic film provided thereon, the reflector can be made lighter and have small inertia, protecting the reflector swinging device from strain.
When the electromagnetic radiator is an injection-molded product made of a magnesium alloy, the electromagnetic radiator can be manufactured in mass production though it has a complicated shape. The electromagnetic radiator can be manufactured so as to be lightweight and have a stable performance at a low cost. This means that the antenna unit according to the present invention can provide a vehicular radar with a stable performance at a low cost.